The equation formed by decreasing each root of ax2+bx+c=0 by 1 is 2x2+8x+2=0, then

α, β be the roots of ax2+bx+c=0∴α+β=-b/a, αβ=c/aNow roots are α-1, β-1Their sum, α+β-2=(-b/a)-2=-8/2=-4Their product, (α-1)(β-1)=αβ-(α+β)+1ca+ba+1=1∵ New equation is 2x2+8x+2=0 also c+b=0⇒b=-c